Year | Value | 2022 | 17.98 | 2021 | 17.695 | 2020 | 17.427 | 2019 | 17.174 | 2018 | 16.937 | 2017 | 16.714 | 2016 | 16.506 | 2015 | 16.313 | 2014 | 16.132 | 2013 | 15.966 | 2012 | 15.812 | 2011 | 15.672 | 2010 | 15.544 | 2009 | 15.429 | 2008 | 15.326 | 2007 | 15.235 | 2006 | 15.144 | 2005 | 15.054 | 2004 | 14.964 | 2003 | 14.875 | 2002 | 14.786 | 2001 | 14.698 | 2000 | 14.61 | 1999 | 14.522 | 1998 | 14.384 | 1997 | 14.002 | 1996 | 13.629 | 1995 | 13.263 | 1994 | 12.907 | 1993 | 12.558 | 1992 | 12.218 | 1991 | 11.885 | 1990 | 11.56 | 1989 | 11.243 | 1988 | 10.934 | 1987 | 10.641 | 1986 | 10.4 | 1985 | 10.163 | 1984 | 9.931 | 1983 | 9.704 | 1982 | 9.481 | 1981 | 9.263 | 1980 | 9.05 | 1979 | 8.841 | 1978 | 8.636 | 1977 | 8.394 | 1976 | 8.015 | 1975 | 7.652 | 1974 | 7.304 | 1973 | 6.97 | 1972 | 6.651 | 1971 | 6.345 | 1970 | 6.053 | 1969 | 5.773 | 1968 | 5.505 | 1967 | 5.249 | 1966 | 5.018 | 1965 | 4.908 | 1964 | 4.8 | 1963 | 4.694 | 1962 | 4.59 | 1961 | 4.489 | 1960 | 4.39 |
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